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The Microbial World

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Title: The Microbial World


1
The Microbial World
  • All three biological domains include microbial
    organisms (or microorganisms)
  • Although microorganisms include some of the
    smallest organisms, they play critical roles in
    the evolution of life on our planet and in the
    ecology of both terrestrial and marine
    environments

Archaea
Bacteria
Animals
Fungi
Plants
Protists
Eukarya
2
The Microbial World
  • Microorganisms are the most important primary
    producers in many marine environments
  • Via photosynthesis and chemosynthesis, they
    manufacture organic matter from CO2
  • As a result, they directly or indirectly feed
    most marine organisms
  • Microorganisms make essential nutrients available
    to other primary producers

3
Viruses
  • Although they may not technically constitute a
    living organism (???), viruses are a critical
    component of the marine food web
  • Viruses are particles made up of nucleic acid
    (RNA or DNA) protected by a protein coat
  • They are parasites that reproduce and develop
    only with the aid of a living cell
  • Viruses are minute, measuring 20-200 nanometers
    (a nanometer is one-billionth of a meter)!

4
You can swim, but you cant hide
  • Viruses are everywhere in the marine environment
  • They parasitize bacteria and plankton (and
    everyone else) releasing organic matter into the
    ocean
  • Provides organic compounds to be grazed upon by
    other members of the microbial community
  • Releases nutrients which may be used by
    photosynthetic organisms
  • May be responsible for half of the bacterial
    mortality in aquatic ecosystems and substantial
    amounts in phytoplankton

5
Viruses
  • The amount of viruses in a given environment is
    directly related to the abundance of the
    microbial life, which they invade
  • Viruses are now recognized as the most abundant
    biological organisms in the ocean
  • For every liter of Long Island Sound water, there
    are 100,000,000,000 viruses!
  • Way more abundant and important than
    previously-believed to be

6
Prokaryotes
  • Prokaryotes are the smallest and structurally
    simplest true-living organisms, and the oldest
    life forms on Earth
  • Prokaryotes are unicellular organisms which lack
    a nucleus and other membrane-bound organelles
    found in eukaryotes
  • Prokaryotes include all members of Domains
    Archaea and Bacteria

7
Bacteria
  • Bacteria (Domain Bacteria) appear to have
    branched out very early on the tree of life and
    are genetically distinct from Archaea and
    eukaryotes (Domain Eukarya)
  • They are abundant in all parts of the ocean
  • Bacteria are vital to life on Earth
    because they ensure the recycling
    of essential nutrients in oceanic
    food webs

8
Bacteria
  • Most organic matter is decomposed by bacteria
  • Bacteria constitute a major part of the organic
    matter that feeds countless bottom-dwelling
    animals
  • Organic particles sinking in the water column are
    composed mostly of bacteria!
  • Very important food source!

9
Marine Snow
  • Marine snow is a continuous shower of mostly
    organic detritus falling from the upper layers of
    the water column
  • Detritus is non-living particulate organic
    material, and is typically colonized by
    communities of microorganisms
  • Includes dead or dying animals
    and plants, phytoplankton, fecal
    matter, sand, soot and dust

http//www.noc.soton.ac.uk/obe/personal/rsl/Rsl_we
b.htm
10
Marine Snow
  • A single cell sinks at a rate of 1-2 meters
    day-1
  • Aggregates sink 150-200 meters day-1
  • Sinking cleanses pollutants from surface waters
    and brings much-needed nourishment to deep sea
    organisms
  • Sediment traps capture sinking debris
  • Flux of particulate matter mirrors productivity
    at the surface peak separated by 2 weeks

11
Feeling small?
  • Particulate matter is defined as anything larger
    than 0.2µm
  • Anything smaller is considered to be dissolved
  • Particulate organic matter is only 10 of the
    total organic material in the ocean dissolved
    organic matter makes up the rest (90)
  • Of all the fish, all the whales, all the
    bacteria, all the organic debris in the oceans,
    90 of it is dissolved
  • Viruses are considered to be dissolved organic
    material

12
Bac(k) to Bacteria
  • Bacteria feed primarily on dead organic material
  • Some bacteria, however, are photosynthetic, the
    cyanobacteria
  • Cyanobacteria have chlorophyll as well as a
    bluish pigment called phycocyanin
  • blue-green algae
  • Among the first photosynthetic organisms

13
Bacteria
  • Cyanobacteria are widely distributed
  • Because of their size, cyanobacteria are believed
    to be the most abundant photosynthetic organisms
    in the ocean
  • In addition to being free-living, some bacteria
    have evolved to live in close association with
    other marine organisms
  • Symbiotic bacteria

14
Symbiotic Bacteria
  • Many of the organelles found in eukaryotic
    organisms evolved from symbiotic bacteria
  • Examples of symbiotic bacteria include those
    involved in the digestion of wood by shipworms,
    those responsible for bioluminescence and those
    found in association with mussels, clams and
    tubeworms that live around hydrothermal vents

15
Symbiotic Bacteria
Shipworms (Teredo) are actually wood-eating
bivalve molluscs!
http//www.divernetxtra.com/biolog/pics/0900flash1
.jpg
bioweb.uwlax.edu/zoolab/lab-5a/mollusca-bivalvia-7
.htm
Bacteria sheltered in light-emitting photophores
of flashlight fish
Tetrodotoxin produced by bacteria in (immune)
pufferfish
16
Archaea
  • Archaea (Domain Archaea) are among the simplest,
    most primitive forms of life
  • Oldest fossils ever found (3.8 billion years old)
    appear similar to Archaea
  • Archaea are prokaryotes, unicellular organisms
    that lack a nucleus and other membrane-bound
    organelles
  • Thought to have had an important role in the
    early evolution of life

17
Three Domains of Life
18
Archea - Extremophiles
  • Some groups of Archaea were discovered only
    recently
  • First in extreme environments on land hot
    sulfur springs, saline lakes, and highly acidic
    or alkaline environments
  • Extremophiles

http//www.dpchallenge.com/image.php?IMAGE_ID4485
61
19
Archaea
  • Archaea were subsequently found in extreme marine
    environments, such as in very deep water, where
    they survive at pressures of 300-800 atmospheres
  • Some archaea live at the high temperatures of
    hydrothermal vents, and cannot grow in
    temperatures under 70-80C (158-176F) 1
    hydrothermal vent archaeum can live at 121C
    (250F) the highest of any known organism

20
Evidence for life on Earth?
  • Many of the harsh conditions which extremophiles
    require to survive were characteristic of our
    early Earth
  • Likely that Archaea evolved to dwell in such
    conditions billions of years ago survive today
    in similar (specific) environments

21
Got Chemosynthesis?
  • Not all prokaryotic autotrophs derive energy from
    photosynthesis (although most do)
  • Some bacterial autotrophs called chemosynthetic
    derive energy not from light, but from chemical
    compounds
  • Hydrogen sulfife (H2S) and other sulfur, nitrogen
    and iron compounds provide energy to convert CO2
    into organic matter
  • Base of food web at hydrothermal vents

22
I need to vent about something here
  • The hot water emerging from hydrothermal vents is
    rich in hydrogen sulfide (H2S) which is toxic to
    most organisms, but an energy-rich molecule
  • Water near the vents
    contain so many

    microbes that they
    cloud the water!
  • Symbiotic and
    non-symbiotic

23
biology.kenyon.edu/sloncbio3/symbiosis.html
24
Anaerobics class
  • Of the heterotrophic prokaryotes, not all use
    oxygen to respire
  • Anaerobic bacteria and archaea grow where oxygen
    is not present, such as anoxic sediments, and are
    actually killed by even small doses of oxygen!
  • These anaerobes use sulfate, and other reduced
    molecules instead of oxygen to respire
  • Responsible for rotten-egg smell of some areas

25
Microbial Eukaryotes
  • There are 7 possible metabolic reactions in
    prokaryotes (photosynthesis, anaerobic aerobic
    respiration, chemosythesis, etc) but only 2 in
    eukaryotes (respiration and photosynthesis)
  • While all prokaryotes are unicellular, eukaryotes
    (possess a nucleus and other membrane-bound
    organelles) are unicellular and/or multicellular
  • Domain Eukarya

26
Microbial Eukaryotes
  • Most microbial marine eukaryotes belong to the
    Kingdom Protista

27
Kingdom Protista (the Protists)
  • Kingdom Protista is the trouble-maker of the
    classification system
  • Can be autotrophic or heterotrophic
  • Can be unicellular or multi-
    cellular
  • But all are
    eukaryotic!
    (Domain Eukarya)

Protists
28
Protists
  • Debates over classification persist
  • Different groups possess different evolutionary
    histories
  • Some are more plant-like (e.g., multi-cellular
    seaweeds)
  • Some are more animal-like (e.g., heterotrophic
    and mobile)
  • Some are photosynthetic and heterotrophic (what
    we call mixotrophic)

29
Algae
  • Algae are a diverse group of protists
  • Nearly all algae perform photosynthesis using
    photosynthetic pigments
  • As protists, algae are distinct from plants and
    lack a cell wall, specialized tissues, and
    flowers
  • They also lack true leaves, stems and roots
  • Unicellular and multi-cellular
  • Multicellular algae are seaweeds!

30
Plants evolved from green algae (which is now
considered a plant, not a protist!)
31
Unicellular Algae The Diatoms
  • Diatoms are unicellular, although many species
    aggregate to form chains
  • Diatom cells are enclosed by cell walls made of
    silica this glassy shell or frustule consists of
    2-tightly fitting halves

32
Diatoms
  • The glass frustule allows light to pass through
    so that photosynthetic pigments can capture light
    energy for photosynthesis
  • UV protection?
  • Aid in sinking?
  • Protection from predation?

33
Diatoms
  • Diatoms are very important primary producers in
    temperate and polar regions
  • Account for a large share of the organic carbon
    produced on Earth
  • Favorable environmental conditions (light snf
    nutrients) promote periods of rapid reproduction
    known as blooms
  • The glass frustules of dead diatoms eventually
    settle to the sea floor diatomaceous ooze

34
Dinoflagellates
  • Dinoflagellates are another important group of
    planktonic, unicellular protists
  • Two flagella one wrapped along a groove along
    the middle of the cell, the other trailing free

35
Dinoflagellates
  • Dinoflagellates may be autotrophic, heterotrophic
    or both (mixotrophic)!
  • Nearly all dinoflagellates are marine
  • Important primary producers, especially in
    tropical regions
  • Some species release toxic substances and can
    cause harmful red tides
  • And some are bioluminescent

36
Dinoflagellates
  • In addition to blooms of red tide, some
    dinoflagellates release toxins responsible for
    open sores on fish, crustaceans and bivalves

37
Zooxanthellae
  • A group of dinoflagellates called zooxanthellae
    live in close association with animals such as
    coral, sea anenomes, sponges and giant clams
  • Symbiotic zooxanthellae photosynthesize within
    the body of an animal host, releasing organic
    matter and receiving nutrients (in the form of
    waste products) and shelter in return
  • Loss of the colorful zooxanthallae is behind the
    phenomenon of coral bleaching

38
www2.watertown.k12.wi.us/pagesfifth_grade_websites
.cfm
www.cgrer.uiowa.edu/peoplecarmichael/atmos_course/
ATMOS_PROJ_99/jlmichfin/main.html
39
Corals (and zooxanthellae) are stressed by
environmental change
  • A water temperature change of only 1C above the
    normal summer high temperature for a few weeks
    leads to coral bleaching
  • Coral expels zooxanthellae or the zooxanthellae
    expels itself
  • El Niño events can drive coral bleaching
  • May be reversible corals can re-acquire new
    zooxanthellae if the stress is not too severe

40
Coccolithophorids
  • Coccolithophorids are unicellular protists
    covered with ornamental plates made of calcium
    carbonate (CaCo3)
  • Form seasonal blooms in North Atlantic
  • Produce dimethyl sulfide, which alters climate
    patterns!
  • Long considered to be the
    smell of the sea

41
Coccolithophorids from space!
42
Foraminiferans
  • Foraminiferans (forams) are marine protists
    that also have a shell made of CaCo3
  • Animal-like possess pseudopodia extensions of
    the cytoplasm used for trapping diatoms and other
    suspended material in the water
  • Benthic or planktonic
  • Important indicators of past
    climate change
  • Form foraminiferous oozes

43
Radiolarians
  • Radiolarians are planktonic marine protists that
    secrete elaborate shells made of silica and other
    materials
  • Cells are typically spherical with radiating
    spines
  • Animal-like
    with

    pseudopodia
  • Radiolarian
    ooze!

http//micro.magnet.fsu.edu/micro/gallery/radiolar
ians/radiohead.jpg
44
Ciliates
  • Ciliates are protists with many hair-like cilia
    used in locomotion and feeding
  • Planktonic or benthic
  • Tintinnids are common ciliates that build
    vase-like cases or loricas made up
    tiny particles such as sand grains
  • Important grazers in the microbial
    loop!

45
And finally
  • Fungi are eukaryotic organisms belonging to the
    Kingdom Fungi
  • All are heterotrophic
  • Can be unicellular or multicellular
  • 1,500 known species of marine fungi
  • Absorb nutrients from their environment
  • Important decomposers in the marine environment,
    but also parasitic (disease-causing)

46
Marine Fungi
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